Connector assembly for use with medical devices

ABSTRACT

Connector assemblies for use with implantable medical devices having easy to assemble contacts are disclosed. The connector assemblies are generally formed by coupling a plurality of ring contacts, sealing rings, and spring contact elements together with at least one holding ring to form a connector having a common bore fore receiving a medical lead cable. Contact grooves or spring chambers for positioning the spring contact elements are formed in part by assembling multiple components together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is an ordinary application of provisional application No.60/910,765, filed Apr. 9, 2007, entitled Connector Assembly for Use withMedical Devices; of provisional application No. 60/911,161, filed Apr.11, 2007, entitled Integrated Header Connector System; and ofprovisional application No. 61/024,660, filed Jan. 30, 2008, entitledIn-Line Connectors; the contents of each of which are expresslyincorporated herein by reference as if set forth in full.

A connector assembly having one or more conductive elements inspaced-apart configuration is generally discussed herein with particulardiscussions extended to connector assemblies for use with implantablemedical devices having easy to assemble contact elements.

BACKGROUND

Implantable medical devices for providing electrical stimulation to bodytissues, for monitoring physiologic conditions, and for providingalternative treatments to drugs are well known in the art. Exemplaryimplantable medical devices include implantable cardio defibrillators,pacemakers, and programmable neuro-stimulator pulse generators, whichare collectively herein referred to as “implantable medical devices” orIMDs. These IMDs typically incorporate a hermetically sealed deviceenclosing a power source and electronic circuitry. Connected to thesealed housing, also known as a “can,” is a header assembly. The headerassembly includes electrical contact elements that are electricallycoupled to the electronic circuits or to the power source located insidethe can via conductive terminals or leads. The header assembly providesa means for electrically communicating, via an external medical leadcable, between the electronic circuits or power source located insidethe device and the actual stimulation point.

Industry wide standards have been adopted for, among other things, thedimensions, size, pin spacing, diameter, etc. for the receptacle and themedical lead cable. Furthermore, good electrical contact must bemaintained during the life of the implantable medical device, and themedical lead cable for use with the IMD must not disconnect from thereceptacle located in the header, yet be detachable for implanting andprogramming purposes and for replacing the IMD when necessary.

Although prior art connector contacts provide viable options for medicaldevice manufacturers, the overall dimensions of existing receptaclespose manufacturing challenges. Among other things, placing stackablerings in between electrically insulating seals, positioning conductivecontact elements in between conductive grooves for forming a receptacleand integrating the contact assembly into the IMD are difficult, costlyand time consuming tasks. Accordingly, there is a need for a receptaclethat not only meets the challenges associated with implantableapplications but is also easier to manufacture than a variety ofexisting receptacles. There is also a need for a receptacle that iseasily adaptable with existing implantable medical devices that areeasier to manufacture than a variety of existing implantable medicaldevices.

SUMMARY

Aspects of the present invention includes an implantable medical devicecomprising a header attached to a sealed housing. A connector assemblyis disposed in the header and comprises a ring contact element having awall structure comprising an interior wall surface and an exterior wallsurface; the ring contact element being electrically conductive. A firstseal ring comprising a wall structure comprising an exterior wallsurface and an interior wall surface having an annulus comprising aninside diameter; a second seal ring comprising a wall structurecomprising an exterior wall surface and an interior wall surface havingan annulus comprising an inside diameter; and wherein the first sealring and the second seal ring overlap the ring contact element such thatthe exterior wall surface of the ring contact element contacts theinterior wall surface of both the first seal ring and the second sealring. A spring contact element is positioned in a spring chamber formedby the interior wall surface of the ring contact element and two sidewalls each formed from an electrically insulative material.

Optionally, one of the two side walls of the medical device is definedby the annulus of the first seal ring and the other one of the two sidewalls is defined by the annulus of the second seal ring.

As provided, the ring contact element may have a generally constantinside diameter throughout the interior wall surface.

A further aspect of the present invention includes modifying the annulusof the first seal ring to have two tapered edges defining a lip.

For a longer connector, a further aspect of the present inventionincludes incorporating a second ring contact element in contact with theinterior wall surface of the first seal ring.

In yet another aspect of the present invention, there is provided animplantable medical device comprising a header attached to a sealedhousing and having a connector assembly disposed in the headercomprising two ring contact elements each comprising a wall structurecomprising an interior wall surface and an exterior wall surface; thetwo ring contact elements being electrically conductive. A seal ringcomprising a wall structure comprising an exterior wall surface and aninterior wall surface having an annulus comprising an inside diameter isincorporated wherein the seal ring overlaps the two ring contactelements such that the exterior wall surfaces of the two ring contactelements each contacts the interior wall surface the seal ring. The twospring chambers, each comprising a back wall and two side walls, aredefined, at least in part, by the interior wall surfaces of the two ringcontact elements and the annulus of the seal ring.

In accordance with aspects of the present invention, the seal ring ismay be made from an electrically insulative material.

In yet another aspect of the present invention, a connector assembly isprovided comprising a first end seal near an opening to the connectorassembly; a second end seal on an end of the connector assembly oppositethe first end seal; a plurality of ring contact elements disposed inbetween the first end seal and the second end seal; and a plurality ofseal rings disposed in between the first end seal and the second endseal. At least one of the ring contact elements is disposed in betweentwo seal rings and in sealing arrangement with the two seal rings. Theplurality of ring contact elements each comprises a centerline along aradial direction, which divides the ring contact element into a firstring section and a second ring section, and wherein the first ringsection and the second ring section are not symmetrical.

In yet another aspect of the present invention, there is provided amethod for forming a cavity for retaining a spring in a connector for amedical device comprising providing an electrically conductive ringcontact element comprising a wall surface, a groove, and a single sidewall singularly formed with the wall surface, said single side wallcovering a first side of the groove; placing an electrically insulativeseal ring in adjacent contact with the electrically conductive ringcontact element; said seal ring providing a wall surface for a secondside of the groove; placing a spring into the groove; and wherein thespring is retained by the single side wall and the wall surface of theseal ring such that the spring is restricted along an axial direction bythe single side wall and the wall surface.

An additional aspect of the present invention is an implantable medicalconnector stack having easy to install ring grooves for receivingcontact springs comprising: a first seal element made of a dielectricmaterial comprising an annulus comprising a projection; said annuluscomprising a generally planar wall surface; a conductive ring contactelement comprising an interior wall surface adjacent at least one axialopening; a second seal element made of a dielectric material comprisingan annulus comprising a projection; a canted coil spring; wherein theconductive ring contact element is engaged to the first seal element andthe second seal element and a ring groove is formed by at least one ofsaid engagements; and wherein the generally planar wall surface of thefirst seal element forms a dielectric side wall of the ring groove thattogether with the interior wall surface of the conductive ring contactelement define a physical stop for retaining the canted coil springinside the ring groove.

A still additional aspect of the present invention is an implantablemedical connector stack having easy to install ring grooves forreceiving contact springs comprising: a conductive ring contact elementcomprising a first axial side and a second axial side; a firstdielectric seal element in mechanical engagement with the first axialside of the conductive ring contact element; a second dielectric sealelement in mechanical engagement with the second axial side of theconductive ring contact element; and wherein a ring groove foraccommodating a canted coil spring is formed by the engagements betweenthe conductive ring contact element and the first and second dielectricseal elements; and wherein at least part of the ring groove has a firstside wall formed by at least one of the first dielectric seal elementand the second dielectric seal element.

Aspects of the present invention further includes a method for formingan implantable medical connector stack having easy to install ringgrooves for receiving contact springs. In one embodiment, the methodcomprises the steps of positioning a canted coil spring into aconductive ring contact element; positioning the conductive ring contactelement into engagement with a first dielectric seal element;positioning the conductive ring contact element into engagement with asecond dielectric seal element; wherein a groove comprising a bottomwall and two side walls is formed by the engagement between theconductive ring contact element and at least one of the first and seconddielectric seal elements; and wherein at least one of the two side wallsis formed by part of the first dielectric seal element or the seconddielectric seal element.

An additional aspect of the present invention is a method for forming animplantable medical connector stack having easy to install ring groovesfor receiving contact springs. The method comprises: forming a ringgroove by sliding a conductive ring contact element and two dielectricseal elements onto an installation rod and into axial engagement withone another; and placing a canted coil spring into the ring groove byplacing the canted coil spring onto the installation rod and sliding thecanted coil spring under a bottom wall defined by the conductive ringcontact element.

In yet another aspect of the present invention, there is provided amethod for forming an implantable medical connector stack having easy toinstall ring grooves for receiving contact springs. The methodcomprising: projecting two axial ends of a conductive ring contactelement over two shoulders of two adjacent non-conducting seal elementsor under two shoulders of two adjacent dielectric seal elements to forma ring groove comprising a bottom wall made of a conductive material andtwo side walls each made from a non-conductive material; and placing acanted coil spring into the ring groove before the conductive ringcontact element projects over or under at least one of the two adjacentnon-conducting seal elements.

In still yet other aspect of the present invention, a method for forminga connector stack for an implantable medical device having reducedoverall length is provided. The method comprising inserting a tubularring contact element into two adjacent seal ring elements to form a ringgroove, and placing a spring into said ring groove.

Other aspects and variations of the connector assemblies summarizedabove are also contemplated and will be more fully understood whenconsidered with respect to the following disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric cut-away view of a connector assemblyprovided in accordance with aspects of the present invention, whichcomprises a plurality of seal rings, contact rings, and spring contactelements.

FIG. 2 is an isometric cut-away view of the connector assembly of FIG. 1in an assembled state with a medical lead cable disposed in theconnector bore.

FIG. 3 is an isometric view of the connector assembly of FIG. 2.

FIG. 4 is an isometric transparent view of the connector assembly ofFIGS. 1-3 inside a header and atop a sealed housing of an implantablemedical device.

FIG. 5 is an exploded isometric cut-away view of an alternate embodimentof a connector assembly provided in accordance with aspects of thepresent invention, which comprises a plurality of seal rings, contactrings, and spring contact elements.

FIG. 6 is a cross-sectional schematic partial view of a seal ring,contact ring and spring contact element according to aspects of thecurrent invention.

FIG. 7 is an isometric cut-away view of the connector assembly of FIG. 5in an assembled state with a medical lead cable disposed in theconnector bore.

FIG. 8 is an isometric view of the connector assembly of FIG. 7.

FIG. 9 is an isometric cut-away view of an alternate embodiment of aconnector assembly in an assembled state including seal rings havingdouble lip seal configuration.

FIGS. 10-11 show yet another alternative connector assembly inaccordance with aspects of the present invention.

FIG. 12 is an alternative configuration of the connector assembly ofFIGS. 10-11.

FIGS. 13-15 show yet another alternative connector assembly inaccordance with aspects of the present invention.

FIGS. 16-17 show still yet another alternative connector assembly inaccordance with aspects of the present invention.

FIGS. 18-19 show yet another alternative connector assembly inaccordance with aspects of the present invention.

FIG. 20-21 show yet another alternative connector assembly in accordancewith aspects of the present invention.

FIG. 22-23 are schematic views of a connector stack being placed in apre-formed header comprising a cavity for accommodating the stack.

Other aspects and features of the receptacles provided herein may bebetter appreciated as the same become better understood with referenceto the specification and claims.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of the presently preferredembodiments of connector assemblies or stacks for electricallycommunicating with medical leads or conductive terminals. The leads inturn connect to integrated circuits, a power source, and/or circuitchips located inside a sealed medical implantable device. The connectorassemblies provided in accordance with aspects of the present inventionare not intended to represent the only forms in which the presentinvention may be constructed or utilized. The description sets forth thefeatures and the steps for constructing and using the connectorassemblies of the present invention in connection with the illustratedembodiments. It is to be understood that the same or equivalentfunctions and structures may be accomplished by different embodimentsand are also intended to be encompassed within the spirit and scope ofthe present invention, especially those incorporating a combination offeatures shown in the different embodiments included herein. As denotedelsewhere herein, like element numbers are intended to indicate like orsimilar elements or features.

Referring now to FIG. 1, an exploded isometric cut-away view of aconnector assembly or implantable medical connector stack provided inaccordance with aspects of the present invention is shown, which isgenerally designated 10. The connector assembly 10 is configured toreceive a medical lead cable 12, which has a proximal end 13 comprisinga proximal tip 14, having a recessed section or groove 17 for acceptinga set screw or other lead locking device, and a plurality of electricalterminals 16 interposed in between lead insulators 18. The lead cable 12further comprises a lead body 20 for carrying a plurality of electrodeleads 22 from between the proximal end 13 and a distal end (not shown),which has electrode terminals for providing electrical stimulation tothe body tissues. The number of electrode leads 22 and correspondingnumber of electrical terminals 16 can vary depending on the particularimplant application, which also determines the number of electrical ringcontacts in the connector assembly 10, as further discussed below.Accordingly, applications of the connector assemblies discussed hereininclude unipolar, bipolar, and multi-polar applications by simplychanging the number of components used to make the connector assembly.

In one exemplary embodiment, the connector assembly 10 comprises aplurality of non-conductive seal rings 24, conductive ring contactelements 26, and spring contact elements 28. Together with a holdingring 30, the plurality of seal rings 24, ring contact elements 26, andspring contact elements 28 form the basic components of the connectorassembly 10 of the present embodiment, which has a common bore forreceiving the proximal end of the lead cable 12. Broadly speaking, theseal rings 24 are each configured to seal, along its internal diameter,against the lead cable 12 and, along the outer periphery of its exteriorshoulders, adjacent ring contact element(s) 26. As is readily apparentto a person of ordinary skill in the art, bodily fluids should beprevented from traveling along the lead cable 12 into the connectorassembly or in through the seams between the contact ring element 26 andtwo adjacent seal rings 24. The ring contact elements 26 are eachconfigured to pass an electric current or signal from a conductor 36located inside an IMD housing to a corresponding spring contact element28, which then passes the electric current or signal to a correspondingelectrical terminal 16 on the lead cable 12 then onto a correspondingelectrode lead 22 located inside the lead body 20 and to a correspondingelectrode terminal on the distal end of the lead cable. The samefunction is accomplished when the connector contacts are used as anExtension, which is the primary electrical connection used duringimplant surgery.

In accordance with aspects of the present invention, two sub-classes ofseal rings 24 are incorporated, which include an end seal ring 32 and anintermediate seal ring 34. The end seal ring 32 comprises a singleexternal shoulder 38 for projecting into an adjacent bore 40, whichcould be that of a contact ring 26 or otherwise. The intermediate sealring 34 comprises two external shoulders 38 for projecting into twoadjacent bores 40, which could be that of two different contact rings 26or otherwise, such as one contact ring 26 and a holding ring 30.However, an intermediate seal ring 34 can be used in place of an endseal ring 32 without deviating form the spirit and scope of the presentinvention.

With reference to FIG. 2 in addition to FIG. 1, when two adjacent sealrings 24 engage the bore 40 of a common contact ring element 26, acontact groove 42 is formed for accommodating a spring contact element28. The spring contact element 28, which is preferably a radial or axialcanted coil spring commercially available along with the seals from BalSeal Engineering of Foothill Ranch, Calif., is sized so that it ispositioned by the groove along its two axial ends and establishescontact along its outer and inner radial circumference. Its internaldiameter 44 is preferably smaller than the internal diameter 46 of theseal ring 24, which is slightly smaller than the outer diameter of theproximal end 13 of the lead cable 12. In other words, when the proximalend 13 of the lead cable 12 is inserted into the common bore, the leadcable has a slight interference fit with the plurality of seal rings 24and the canted coil springs 28. The seal rings 24 are also ininterference fit with the adjacent bores along their respective externalshoulders 38 to facilitate assembly of the various components.

The spring contacts 28 are similarly sized so that each is deflected bythe lead cable 12 to about 5% and up to about 50% of its total radialdeflection with up to about 40% being more preferred. This deflectionrange ensures a sufficient spring contact force is generated between thecontract rings 26 and the electric terminals 16 on the lead cable 12 fortransferring electric current or signals between the two.

Referring again to FIG. 1, in one exemplary embodiment, the contactrings 26 are each generally cylindrical in configuration. Morepreferably, each contact ring 26 has a generally constant inner diameterand outer diameter with two square ends, with normal manufacturingtolerance being acceptable. Said differently, the contact rings 26 donot have machined or formed grooves for forming contact grooves thereinfor accommodating the spring contact elements 28. The contact rings 26have a simple profile, which in one embodiment is tubular in shape andmakes manufacturing the rings and assembling the spring contacts 28therein easier and therefore more cost effective. The contact groovesare formed instead by a combination of adjacent seal rings 24 and theinner surface of the ring contact element 26. While FIG. 1 is the morepreferred design, alternative contact ring internal geometries arepossible in the area of contact with the spring without compromisingease of assembly for the spring 28 and contact ring. For example, thecontact ring inside diameter can have a “v” shaped groove geometry inthe area of the spring contact so that two points of contact areavailable with the spring versus one.

Other geometries are also contemplated. For example, the contact ring 26may have a thicker section so that there are at least two internaldiameters. The spring contact element 28 can then be inserted throughthe larger internal diameter end of the contact ring 26 until it abutsthe shoulder formed at the intersection between the two differentinternal diameters. Thus, different diameters and undulating internalsurfaces for the contact rings are contemplated. The ring with av-shaped groove can be considered a sub-species of a ring having atleast two internal diameters. Still alternatively, the plurality ofcontact rings in a single connector assembly may vary, i.e., are notuniform. For example, it is possible to use a ring with a “v” shapedgroove at the distal most end of the connector assembly and rings with asmoother contour as shown in FIG. 1 for the remaining contact rings.Still alternatively, a ring with two different internal diameters may beused with the ring having a v-shaped groove and with rings having auniform internal diameter. If a contact ring having two differentinternal diameters at its two ends is used, the seal rings 24 aremodified accordingly to engage the different internal diameters of thecontact ring. Thus, contact rings provided herein not only can have asmooth internal diameter, but also machined surfaces and undulatingsurfaces.

Thus, in accordance with one aspect of the present invention, there isprovided a method for assembling a plurality of components to form aconnector assembly or stack comprising engaging a first seal ring 34 toa holding ring 30, engaging a first contact ring 26 with the first sealring 34, placing a first spring contact element 28 inside the firstcontact ring, and engaging a second seal ring 34 with the first contactring to form a ring groove for constraining the first spring contacttherein. The method further comprises steps that include adding otherseal rings, contact rings, and spring contact elements to form aconnector assembly having a desired number of contact grooves. Morepreferably, the method further comprises the steps of assembling aconnector assembly without having to utilize a tool or by hand or bysecondary assembly processes manipulate, compress, bend, or distort aspring contact to fit within a contact groove. The assembled connectorassembly is typically then placed into a mold cavity and over-moldedwith an implantable grade polymer or elastomer, such as epoxy orsilicone. The connector assembly can also be inserted into a pre-moldedheader, which resembles a housing having a cavity for receiving theconnector assembly and one or more openings for placing the connectorassembly into the pre-molded header. The one or more openings are thenbackfilled or sealed, typically after attaching or welding theconductors from the sealed housing to the contact rings, to complete theassembly.

In accordance with other aspects of the present invention, there isprovided an alternative method for assembling a connector assembly inwhich a dowel or assembly pin (not shown) is used, which resembles theproximal end 13 of the lead cable 12 shown in FIG. 1. The assembly pin(not shown) is used to construct the connector assembly 10 by firstplacing a holding ring 30 on an end of the assembly pin and thensubsequently placing other components on the pin and then sliding theminto engagement with the earlier placed components. The assembledcomponents, i.e., the connector assembly or stack, may then be securedby placing the same inside a cavity and over-molding the assembly withan implantable grade polymer or elastomer.

In the embodiment shown, the holding ring 30 functions as an end cap andhas an end wall 46 and a shoulder 48 for mating engagement with theshoulder on the seal ring 34. A threaded bore 50 for receiving a setscrew 52 is incorporated in the holding ring 30 to more securely fixingthe lead cable 12 to the connector 10 assembly (FIG. 2). Alternatively,an end holding ring (not shown) may be incorporated at the distal mostend 54 of the connector assembly for providing the locking function onthe lead cable 12. During the over-molding step, a window should beformed around the threaded bore 50 for securing the lead cable, whichcan then be back-filled using a curable and implantable material.

Referring again to FIG. 2, the seal rings 24 of the present embodiment,except for the end seal ring 32, are each symmetrical about a centerlinedrawn perpendicular to the axis defined by the lead cable 12 and throughthe center of the seal ring. However, non-symmetry or otherconfigurations are possible so long as a contact groove foraccommodating a spring contact is formed at least in part by engagingthe contact ring 26 with two adjacent seal rings 24. Furthermore, whilethe seal rings 24 of the present embodiment are shown each comprising aninternal projection 47 for sealing against the lead cable 12, aspreviously discussed, two or more projections may be incorporatedwithout deviating from the spirit and scope of the present invention.Still furthermore, part of the seal ring that projects into the bore ofa contact ring can be made separately. In other words, a seal ring maybe made by co-molding or over-molding two separate components.

Following assembly of the various components to form the connectorassembly 10 shown in FIG. 2, the connector assembly is encased inside animplantable elastomer or polymer layer, as previously discussed. Theconnector assembly 10 is preferably molded with an assembly pin locatedinside the common bore to ensure alignment, both radially and axially,of the various connector components. The encased connector may bereferred to as a connector header, for placing on a can or sealedhousing of an IMD. In one exemplary embodiment, windows (not shown) areleft exposed through the over-molded layer adjacent each contact ring26. When the header is placed over the can, a plurality of contactconductors 36 in communication with a power source and/or electroniccircuits inside the can project upwardly into physical contact with thecontact rings 26. The contact conductors 36 may then welded to acorresponding contact ring 26 to ensure good electrical contact throughthe windows. The windows are then backfilled and sealed using curableimplantable elastomer or polymer.

FIG. 3 is a fully assembled view of the connector assembly 10 of FIGS. 1and 2 with the medical lead cable 12 disposed inside the common bore. Ascan be appreciated, the connector stack 10 provided herein allows forthe distance between one ring contact element and an adjacent ringcontact element to be reduced. The reduction is facilitated by, amongother things, eliminating metallic side walls for capturing the springsinside the ring grooves. Thus, the overall length of the stack, from theholding ring 30 to the distal end most seal element 24, may be reducedcompared to connector stacks having metallic side walls for capturingthe springs. Accordingly, a method is provided for forming a connectorstack having reduced overall length comprising inserting a tubular ringinto two adjacent seal ring elements to form a ring groove, and placinga spring into said ring groove. Advantageously, the stack provided inaccordance with aspects of the present invention reduces manufacturingand installation costs, simplifies assembly, and shortens the overalllength of the stack to allow for smaller sized IMDs.

Referring now to FIG. 4, an IMD 56 incorporating a connector assembly 10provided in accordance with aspects of the present invention is shown.The connector assembly 10 is shown in a header 58, which is shown as atransparent material or structure for purposes of discussion. Inpractice, the overcoat or over-molding layer is more commonlysemi-opaque or opaque. The header 58 is situated over a can 60, which ishermetically sealed with a power source and electronic circuits. Aspreviously discussed, the IMD can be any one of plurality of IMDs formedical treatment, monitoring, or diagnostics.

Also shown in FIG. 4 are weld traces 62 for welding the conductors 36 tothe contact rings 26. Typically, the conductors 36 project through oneor more feed through terminals that pass through the hermetically sealedhousing or can 60 to contact the contact rings 26. Although a singleconnector assembly 10 is shown inside the header 58, two or moreconnector assemblies 10 may be used if desired depending on theparticular implant application. The connector assemblies may be stackedside-by-side or on top of one another.

With reference now to FIG. 5, in another exemplary embodiment, aconnector assembly 100 comprises a plurality of non-conductive sealrings 124, conductive ring contact elements 126, and spring contactelements 128. Together with a holding ring 130, the plurality of sealrings 124, ring contact elements 126, and spring contact elements 128form the basic components of the connector assembly 100 of the presentembodiment, which has a common bore for receiving the proximal end ofthe lead cable 12. Generally speaking, the seal rings 124 provide a sealalong their interior bore 156 when compressed against the lead cable 12,and along the inner periphery of their interior shoulders 138 againstadjacent ring contact element(s) 126. As is readily apparent to a personof ordinary skill in the art, bodily fluids should be prevented fromtraveling along the lead cable 12 into the connector assembly or inthrough the seams between the ring contact elements 126 and adjacentseal rings 124. The ring contact elements 126 are each configured topass an electric signal from a lead 136 having one end located inside anIMD housing to a corresponding spring contact element 128, which thenpasses the electric signal to a corresponding electrical terminal 16 onthe lead cable 12, then onto a corresponding electrode lead 22 locatedinside the lead body 20 and to a corresponding electrode terminal on adistal end of the lead cable.

In accordance with aspects of the present invention, two sub-classes ofseal rings 124 are incorporated including an end seal ring 132 and anintermediate seal ring 134. The end seal ring 132 comprises a singleinternal shoulder 138 for receiving an adjacent exterior wall surface140 of a ring contact 126 or otherwise. With reference now also to FIG.6, each intermediate seal ring 134 comprises an annulus 137, whichresembles an inwardly protruding flange defining two interior side walls139 defining a lip 156 therebetween, and two internal shoulders 138 forreceiving an adjacent exterior wall surface 140, which could be that oftwo different ring contacts 126 or otherwise, such as one ring contact126 and a holding ring 130. The lip 156 defines an internal bore havingan internal diameter adapted to receive a lead cable, as furtherdiscussed below. In an alternative embodiment, an intermediate seal ring134 can be used in place of an end seal ring 132 without deviating fromthe spirit and scope of the present invention.

In one exemplary embodiment of the present invention, a surface of theannulus or flange 137 has two beveled or tapered edges 145 configured tofacilitate assembly of the connector apparatus or insertion of a leadcable. As is readily apparent to a person of ordinary skill in the art,the tapered surfaces redirect an alignment pin or a lead cable throughthe internal bore of the seal ring when the same come in contacttherewith. In another exemplary embodiment, a seal ring 160 (FIG. 9) hasan annulus or inwardly protruding flange 162 having a double sealing lipconfiguration 164 on its interior bore surface. The alternative sealring comprises four tapered or beveled edges defining two lips. Duringuse, the double sealing lip configuration 164 enhances the sealingability of the seal ring against the lead cable. One skilled in the artwill appreciate that other annulus shapes and lip shapes are possiblewithout deviating from the scope or spirit of the invention.Additionally, although a single flange or annulus is described, multipleflanges spaced from each other may also be incorporated.

With reference now also to FIG. 7, when two adjacent seal rings 124engage the exterior wall surface 140 of a common ring contact element128 such that the ring contact element abuts the interior side walls 139and the interior shoulder 138 of the seal rings 124, a spring chamber142 is formed for accommodating a spring contact element 128. The springcontact element 128, which is preferably a radial or axial canted coilspring commercially available along with the seals from Bal SealEngineering of Foothill Ranch, Calif., is sized so that it is positionedby the groove along its two axial ends and establishes contact along itsouter and inner radial circumference. Its internal diameter 144 ispreferably smaller than an internal diameter defined by the interiorbore 156 of the seal ring 124, which is slightly smaller than the outerdiameter of the proximal end 13 of the lead cable 12. In other words,when the proximal end 13 of the lead cable 12 is inserted into thecommon bore, the lead cable has a slight interference fit with theplurality of seal rings 124 and the canted coil springs. The seal rings124 are also in interference fit with the adjacent external wallsurfaces 140 of the ring contacts 128 along their respective internalshoulders 138 to ensure proper sealing between the various components.In one exemplary embodiment, the ring contacts 128 each comprises awidth that may be greater than a combined depth of two adjacent internalshoulders 138 of two adjacent seal rings 124, thus defining a gap 143between the seal rings 124. The gap 143 allows one end of a lead 136 tobe connected directly to the ring contact element 128.

The spring contacts 128 are similarly sized so that each is deflected bythe lead cable 12 to about 5% and up to about 50% of its total radialdeflection with up to about 40% being more preferred. This deflectionrange ensures a sufficient spring contact force is generated between thecontract rings 126 and the electric terminals 16 on the lead cable 12for transferring electric signals between the two.

Referring again to FIG. 5, in one exemplary embodiment, the ringcontacts 126 are each generally cylindrical in configuration. Morepreferably, each ring contact 126 has a generally constant innerdiameter and outer diameter with two square ends, with normalmanufacturing tolerance being acceptable. In other words, the ringcontacts 126 do not have machined or formed grooves for forming springchambers therein for accommodating the spring contact elements 128. Thering contacts 126 have a simple profile, which makes manufacturing therings and assembling the spring contacts 128 therein easier andtherefore more cost effective. The spring chambers 142 are formedinstead by a combination of interior side walls 139 of adjacent sealrings 124 and the interior wall surface 141 of the ring contact element126. While FIG. 5 is an exemplary design, alternative ring contactinternal geometries are possible, similar to those described above.

In the embodiment shown in FIG. 5, the holding ring 130 functions as anend cap and has an end wall 147 and an exterior wall surface 148 formating engagement with the interior shoulder 138 of a seal ring 134. Theend caps also function to properly compress a stack of connectors suchthat the assembly can be over-molded without leakage of the over-moldingmaterial into the assembly. As is also shown in FIG. 7, a threaded bore150 for receiving a set screw 152 is incorporated in the holding ring130 to more securely fix the lead cable 12 to the connector 100assembly. Alternatively, an end holding ring (not shown) may beincorporated at the distal most end of the connector assembly forproviding the locking function on the lead cable 12.

Referring again to FIG. 7, the seal rings 124 of the present embodiment,except for the end seal ring 132, are each symmetrical about acenterline drawn perpendicular to the axis defined by the lead cable 12and through the center of the seal ring. However, non-symmetry or otherconfigurations are possible so long as a spring chamber foraccommodating a spring contact is formed at least in part by engagingthe ring contact 126 with two adjacent seal rings 124. Furthermore,while the seal rings 124 of the present embodiment are shown eachcomprising an internal projection for sealing against the lead cable 12,two or more projections may be incorporated without deviating from thespirit and scope of the present invention. Still furthermore, part ofthe seal ring that projects over the external surface of a ring contactcan be made separately. In other words, a seal ring may be made byco-molding or over-molding two separate components.

Additionally, in accordance with one aspect of the present invention, amethod is provided for assembling a plurality of components to form aconnector assembly as described above. Following assembly of the variouscomponents to form the connector assembly 10 shown in FIG. 7, theconnector assembly is encased inside an implantable elastomer or polymerlayer, as previously discussed. FIG. 8 is a fully assembled view of theconnector assembly 100 of FIGS. 5 and 7 with the medical lead cable 12disposed inside the common bore.

Thus, aspects of the present invention include steps for assembling amedical connector stack comprising the steps of sliding a conductivering element over a shoulder of each of two adjacent seal elements(FIGS. 1-2) or under a shoulder of each of two adjacent seal elements(FIGS. 5, 9, and 10) to form a ring groove comprising a conductivebottom wall surface and two non-conductive side wall surfaces; andplacing a canted coil spring into the ring groove. A further aspect ofthe present invention is a provision for forming an implantable medicalconnector stack comprising the steps of providing an assembly pin,placing a dielectric seal element onto the assembly pin, placing aconductive ring element onto the assembly pin, placing a canted coilspring onto the assembly pin and inside the conductive ring element;placing a second dielectric seal element onto the assembly; and slidingthe conductive ring element into engagement with the two dielectric sealelements to form a ring groove for retaining the canted coil spring.This method lends itself to ease of assembly of a connector stackincluding automated assembly.

FIG. 10 is a sectional assembled side view of another connector assemblyor stack 180 provided in accordance with aspects of the presentinvention. Like previously discussed connector assemblies, the presentembodiment incorporates similar basic components, namely two end seals182, a plurality of ring contact elements 184, a plurality of seal rings186, and a plurality of canted coil springs 188, which may be an annularradial canted coil spring or an annular axial canted coil spring. Theassembled components have a common bore for receiving a medical leadcable 12.

While the number of end seals 182 per connector assembly 180 aregenerally two, the number of ring contact elements 184, seal rings 186,and canted coil springs 188 may vary depending on the particularapplication, e.g., unipolar, bipolar, or multi-polar application. Asshown, the connector assembly 180 is a multi-polar connector assemblyhaving seven conductive points for electrically coupling with a sevenelectrode medical lead cable 12.

In one exemplary embodiment, the end seals 182 each incorporates twoprojections or annular rings 190 for sealing against a lead insulator toprevent fluid from seeping into the common bore. A square shoulder 192is incorporated to abut against an adjacent contact ring element 184along an axial direction and compresses over the adjacent contact ringin a radial direction, in an interference fit. The shoulder 192 has asufficient depth to receive the adjacent ring contact element 184 yetnot too deep so as to provide a gap 194 with and adjacent seal ringexteriorly so that contact between the ring contact element and acontact conductor 36 could be made. The ends seals 182 and the sealrings 186 are preferably made from a medical grade polymer or elastomer,such as silicone. Thus, as such material is flexible and resilient, arange of interference fit is possible which provides for manufacturingflexibility in terms of tolerance and accuracy.

With reference now to FIG. 10A in addition to FIG. 10, an enlargedsimple cross-sectional side view of a contact ring element 184 engagedto a seal ring 186 is shown. In one exemplary embodiment, the contactring element 184 comprises a cavity 196 for accommodating the cantedcoil spring 188. As shown, the cavity 196 is defined by a cavity base200 that represents an obtuse angle and a side wall 198. Forillustration purposes, the side of the contact ring element with theside wall 198 may be referred to as the first side or closed side 199and the other side without the side wall may be referred to as thesecond side or opened side 201. The single-sided cavity 194 is easier tomanufacture than a similar cavity with two identical or similar sidewalls. Additionally, installation of the coil spring 188 into the cavityfrom the opened side 201 is easier and requires no special tools.

To engage the ring contact element 184 to the adjacent seal ring 186, anaxial projection 202 is incorporated on the opened side 201, which isconfigured to project into a groove 204 on the seal ring 186, in aninterference fit arrangement. The contact ring is made from a conductivematerial and in an exemplary embodiment is made from a steel material,such as medical grade stainless steel, titanium, noble metals such asplatinum or conventional implantable grade materials with noble metalcoatings, such as platinum over stainless steel. The groove 204 isformed on a first wall side 206 of the seal ring 186, which partiallyshields or covers the coil spring 188 on the opened side 201 of thecontact ring 184. In one exemplary embodiment, a clearance or small gapis provided between the first wall side 206 and the spring 188 such thatthe spring does not abut or contact the first wall side during use.However, after insertion of a lead cable 12 and during removal of thelead cable 12, the spring may shift and contacts the first wall side206. Still alternatively, the spring could be sized so that it contactsthe first wall side during normal use.

Like the end seals 182, the seal ring 186 incorporates an annularprojection 190 for forming a seal against a lead insulator on a medicallead cable, similar to previously discussed embodiments. Although asingle annular projection 190 is shown, two or more projections may beincorporated without deviating from the spirit and scope of the presentinvention. Also like the end seals, a square shoulder 192 comprising asecond wall side 208 and an axially extending wall 210 are incorporatedto receive a closed side 199 of an adjacent contact element (shown inFIGS. 10 and 11 but not in FIG. 10A). As the seal ring 186 iscircumferential, the axially extending wall 210 is configured tocompress a contact ring in an interference fit arrangement to provide afluid tight seal along the interface of the two components.

With reference again to FIG. 10, a holding or locking ring 212 isincorporated adjacent an end seal 182. More particularly, as the endseal 182 adjacent the holding ring 212 acts as an entrance to the commonbore of the connector assembly 180, which is an opening for insertion bythe medical lead cable 12, the holding ring 212 may be thought of as afront end locking ring. This locking ring location is configured for usewith a lead cable that has a locking groove 213 located distally of thelast contact ring 186.

In one exemplary embodiment, the locking ring 212 may be made from thesame material as the ring contact element. Alternatively, it could bemade from an implantable grade non-conductive rigid plastic material,such as from PolyEtherEtherKetone (PEEK). The ring 212 has a threadedbore 50 and a set screw 52 for more permanently securing the lead cableto the connector assembly 180.

The components of the connector assembly 180 may be assembled in themanner and fashion as previously discussed for other connectorassemblies. Once assembled, the contact ring elements 184 are eachcompressed along a closed side 199 by a shoulder of one seal ring andcompressed along an opened side 201 by a tongue and groove arrangementto seal the contact ring exteriorly from moisture or fluid. Theassembled connector assembly 180 is then subject to an over-moldingprocess or is inserted into a pre-formed header to retain the assembledcomponents in an assembled state.

FIG. 12 is a sectional assembled view of the connector assembly of FIGS.10-11 in a different configuration. In the present embodiment, theholding ring 212 has been located to the back side 214 of the connectorassembly 216, which is away from the front side or entrance 218 to theconnector assembly for receiving the lead cable 12 into the common bore.This configuration is used for mounting a medical lead cable in whichthe locking groove on the lead cable is located proximally of the firstcontact ring element 184.

FIG. 13 is a sectional assembled view of yet another connector assembly220 provided in accordance with aspects of the present invention. Likethe other connector assemblies, the present connector assembly 220 maybe used with a can as an IMD either in a single connector assemblyapplication (similar to that shown in FIG. 4) or a multi-connectorassembly application in which two or more connector assemblies or stacksare located either in a side-by-side configuration or one on top of theother.

In the embodiment shown, the connector assembly 220 incorporates two endseals 222, a plurality of sealing rings 186, a plurality of ring contactelements 184, and a plurality of canted coil spring 188 interconnectedwith a common bore for receiving a medical lead cable 12, which has aplurality of electrode leads 22. The present embodiment is similar tothe connector assemblies shown in FIGS. 10-12 with the exception of thetwo ends seals 222. Instead of a square shoulder, the two end seals 222each incorporates a groove 204 for receiving an axial projection 202 ofan adjacent ring contact element 184 or, if viewed from the perspectiveof an opposing end seal 222, an axial projection 202 of a locking ring224. The locking ring 224 (FIGS. 13-14) has been modified to incorporatetwo opposing axial projections 202, one for engaging a groove 204 of theend seal 222 and the other for engaging the groove 204 of a seal ring186.

FIG. 15 is a simple enlarged cross-sectional view of a ring contactelement 184 of FIGS. 13 and 14 having its projection 202 inserted into agroove 204 of an end seal 222.

FIG. 16 is a sectional assembled view of yet another connector assembly226 provided in accordance with aspects of the present invention. In oneexemplary embodiment, the connector assembly 226 comprises two endsseals 228, a plurality of ring contact elements 230, a plurality of sealrings 232, a plurality of canted coil springs 188, and a locking ring233. As shown, the ring contact elements 230 are similar to those shownand discussed with reference to FIGS. 10-15 and the locking ring 233 issimilar to that shown and discussed with reference to FIG. 13.

Because the seal rings in the present embodiment are identical, only asingle seal ring will be discussed. In the present embodiment, the sealring 232 is configured to mate with two adjacent contact rings, or onecontact ring and one locking ring, in an over-under configuration. Theseal ring 232 incorporates a reduced outside diameter (OD) section 234for projecting under an axially extending wall section 202 of a contactring element 230. The reduced OD section 234 comprises a first surface236 for an under compression fit arrangement with a contact ringelement, as further discussed below, and a second surface 238 at anangle to the first surface 236 for axially limiting the depth ofinsertion of the reduced OD section 234 into the contact ring element.In an alternative embodiment, the insertion depth is instead controlledby the surface of the partial side wall 240 adjacent the obtuse angledwall of the contact ring element abutting an axial end edge of thereduced OD section.

Once assembled, the axial projection 202 on the contact ring element 230is configured to compress the reduced OD section 234 to provide amoisture and/or fluid tight seal around the exterior surface of thereduced OD section. As is readily apparent to a person of ordinary skillin the art, chamfered edges are preferably incorporated at variouscorners for easy insertion and assembly between the differentcomponents.

In the embodiment shown, the seal ring 232 incorporates a compressionfit section 242 for an over fit arrangement with an adjacent contactring element. In one particular application, the over compression fitsection 242 comprises an axially extending wall 210 and a second wallside 208 that define a square shoulder 192, similar to the squareshoulder incorporated in the seal ring 186 shown and discussed withreference to FIG. 10A. The over compression fit section 242 isconfigured to receive a closed side 199 of an adjacent contact ringelement and compresses that section to form a moisture and/or fluidtight seal. Interiorly, the seal ring incorporates an annular projection190 for forming a interference fit over a corresponding lead insulatorsection of the medical lead cable 12.

FIG. 17 is an isometric view of the connector assembly 226 of FIG. 16.As shown, the connector assembly is configured to receive a lead cable12 with seven-electrode leads 22. However, the connector assembly may bemade with fewer or more components to accommodate a lead cable with adifferent number of electrode leads. Additionally, while the lockingring 233 is shown located at the front end 218 of the connectorassembly, near the opening to the common bore, the locking ring canreadily be placed near the back side to accommodate a lead cable with aproximally located locking groove.

FIG. 18 is yet another connector assembly 244 provided in accordancewith aspects of the present invention. The connector assembly comprisestwo end seals 246, a plurality of ring contact elements 248, a pluralityof seal rings 250, a plurality of canted coil springs 188, and a holdingring or locking ring 251 near the front end or opening of the connectorassembly. In the embodiment shown, the two end seals 246 are similar tothe end seals 182 shown and discussed above with reference to FIGS. 10and 11. The contact rings 248 are also similar to the ring contactelements 184 shown and discussed with reference to FIGS. 10 and 10A withone exception, the present ring contact elements 248 do not incorporatean axial wall section 202 for engaging a groove of an adjacent sealring. Instead, the opened side 201 of each contact ring 248 has agenerally flat but shallower wall than the wall 198 of the closed side199 of the contact element. Said differently, the opened side 201 isdefined by a line drawn radially outwardly from a distal tip of theobtuse angled wall of the cavity. This opened side 201 is configured tobe inserted into an adjacent seal ring 250, as further discussed below.

In one exemplary embodiment, the seal rings 250 of the presentembodiment are generally symmetrical about a centerline drawn throughthe annular projection 190 of each seal ring in a radial direction. Theseal rings 250 each incorporates an axially facing wall side 252 and aradially facing wall side 254 for defining a shoulder 256. The shoulder256 is adapted to receive either the opened side 201 or the closed side199 of an adjacent contact ring element. More specifically, when an endof a contact ring element is received against the shoulder 256, amoisture and/or fluid tight seal is formed exteriorly of the ringcontact element.

As shown in FIG. 19, a gap 258 is provided between two adjacent sealrings 250. As is readily apparent to a person of ordinary skill in theart, the width of the gap 258 may be controlled or regulated by thedepth of the shoulder of the two adjacent seal rings. The gap isprovided to enable a contact conductor 36 from a can or sealed housingof a IMD to be welded to a corresponding contact ring element. Also aspreviously discussed, the number of ring contact elements, canted coilsprings, and seal rings incorporated in the connector assembly 244 mayvary depending on the application, which in turn depends on the type ofmedical lead cable the connector assembly 244 is configured to receive.Still furthermore, the connector assembly 244 may be installed to a canby itself or with one or more other connector assemblies arranged eitherside-by-side or on top of one another.

Thus, in accordance with aspects of the present invention, a method forforming a connector stack is provided wherein a ring groove is formed bya ring contact element having one conductive side wall and onenon-conductive side wall formed by an adjacent dielectric seal element.A further aspect of the present invention is a provision for forming animplantable medical connector stack comprising the steps of providing anassembly pin, placing a dielectric seal element onto the assembly pin,placing a conductive ring element onto the assembly pin, said conductivering element comprising a closed side comprising a side wall and anopened side, placing a canted coil spring onto the assembly pin andinside the conductive ring element through the opened side; placing asecond dielectric seal element onto the assembly; and sliding theconductive ring element into engagement with the two dielectric sealelements to form a ring groove comprising one side wall of a conductivematerial and one side wall of a non-conductive material for retainingthe canted coil spring.

FIG. 20 is an exploded cut-away perspective view of yet anotherimplantable connector assembly or stack 264 provided in accordance withaspects of the present invention. In one embodiment, the connector stack264 comprises, from right to left of FIG. 20, a holding ring 30, andseveral sets of: a seal ring element 24, a ring contact element 266, anda canted coil spring 28. The assembly has one end seal ring 24 locatedat the distal end 54 of the connector stack 264. The number of setsdepend on the particular application of the connector stack. In thepresent embodiment, the stack is configured for use with a three nodelead cable 12 and therefore incorporates three ring contact elements 266and three canted coil springs 28. However, the embodiment and theinvention is not so limited and can vary depending on the particularapplication. In one embodiment, the holding ring 30 and the seal ringelements 24 are the same as the holding ring and seal ring elements ofFIGS. 1-4. Accordingly, only the features of the ring contact elements266 will be discussed.

The ring contact elements 266 each has two axial end openings 268 and aninternal shoulder 270 at each opening. The internal shoulders 270 areeach defined by a lip 272, which is located at an outer edge of aV-groove 274. The ring contact elements 266 may be machined from atubular material or cast molded using conventional molding techniques.The V-groove 274 is configured to axially set and retain a canted coilspring within the bore 40 of the ring contact element and provide atwo-point contact with the spring.

The stack 264 may be assembled by inserting the various components inthe direction of the insertion arrow 276, staring with the holding ring30. In one embodiment, an assembly rod or installation rod (not shown),similar in diameter and shape as the medical lad cable 12, is firstattached to the holding ring 30 by tightening the set screw 52 against agroove located on the assembly rod. The various components are then slidonto the rod and pushed in the direction of the insertion arrow 276. Inother embodiments, the various components are simply inserted in thedirection of the insertion arrow without an assembly rod. Three contactconductors 36 are shown each attached to a contact ring element 266,such as by laser welding. In practice, this usually only occurs afterthe assembled stack 264 is placed into a header of an implantablemedical device (IMD), as further discussed below.

FIG. 21 is a cut-away perspective view of the stack 264 of FIG. 20 fullyassembled and having a medical lead cable 12 inserted into the commonbore. Once the lead cable 12 is inserted, it is secured by tighteningdown on the set screw 52, which clamps down on the groove 17 located atthe proximal end 13 of the lead cable 12 to prevent the lead cable fromaxially backing out of the bore. As shown, the electrical terminals 16on the lead cable 12 align with and contact a corresponding canted coilspring 28. In practice, this allows electrical signals sent through thecontact conductors 36 to pass through the ring contact elements 266,through the canted coil springs 28, and to the electrical terminals 16,which then communicate with corresponding electrode leads 22 locatedinside the medical lead cable 12.

FIG. 22 is an exploded perspective view of an IMD 278, which may be animplantable pulse generator (IPG), which has a can 280 and a header 282,shown in an exploded view along a parting line 284. The header 282comprises an upper header section 286 and a lower header section 288,both of which having a cavity 290 that together form a tight fittingspace for accommodating a medical connector stack 292. The medicalconnector stack 292 in turn receives a medical lead cable 12. In oneembodiment, the connector stack 292 may embody any of the stacksdescribed elsewhere herein, such as the stacks of FIGS. 1-3, 5, 9, 10,12, 13, 16, 18, and 20.

In one embodiment, the upper and lower header sections 286, 288 alsoincorporate cut-outs 294 for providing access to the opening of thecommon bore and to the set screw. The lower header section 288, andoptionally the upper header section 290, also incorporates cut-outs 296for accessing the contact conductors 36. The contact conductors 36project through one or more feed through terminals that pass through thehermetically sealed housing or can 280 to contact the contact rings 296as the stack is placed inside the header, as shown in FIG. 23.

FIG. 23 shows the connector stack 292 situated inside the header 292 andthe two header sections 286, 288 attached to one another along theparting line 284. In one embodiment, the two header sections may beglued or bonded together using any known prior art methods. Eitherbefore or after the two header sections are attached to one another, thecontact conductors 36 are welded to corresponding ring contact elements296. The lead cable 12 is then inserted into the common bore and issecured to the stack by tightening down on the set screw. The cut-outs294 for the contact conductors 294 and the set screw 294 are thenback-filled using implantable grade polymer or elastomer material.

Although limited preferred embodiments and methods for making and usingconnector assemblies provided in accordance with aspects of the presentinvention have been specifically described and illustrated, manymodifications and variations will be apparent to those skilled in theart. For example, various material changes may be used, incorporatingdifferent mechanical engagement means to attach the various componentsto one another, making use of two or more different materials orcomposites, making a sealing ring from multiple pieces rather than asingularly molded piece, etc. Moreover, the connector assembliesprovided herein may be used in conjunction with an Extension, which isused for testing implanted electrode terminals or implanted activatorunits so that programs or controls used to manipulate the implantedelectrode terminals and the like can be programmed for the IMD. Stillalternatively, the connector assembly may be used for any device thatrequires an in-line connection in which multiple conductive sources areto be relayed between a source generator and a source receiver, whetherthat device is configured for implanting or otherwise. Also. whilecertain connector stacks are shown and disclosed for use with a threenode or three electrode terminal lead cable, the number of sealelements, ring contact elements, and canted coil springs are not limitedto the embodiments as shown and can include more or less depending onthe particular application. Accordingly, it is to be understood that theconnector assemblies constructed according to principles of thisinvention may be embodied in other than as specifically describedherein. The invention is also defined in the following claims.

What is claimed is:
 1. An implantable medical connector stack havingeasy to install ring grooves for receiving contact springs comprising: afirst seal element made of a dielectric material comprising an annuluscomprising a projection; said annulus comprising a generally planar wallsurface; a conductive ring contact element comprising an interior wallsurface adjacent at least one axial opening; a second seal element madeof a dielectric material comprising an annulus comprising a projection;a canted coil spring; wherein the conductive ring contact element isengaged to the first seal element and the second seal element and a ringgroove is formed by a bottom wall of the conductive ring contact elementand two side walls formed from one each of the first and second sealelements; and wherein the generally planar wall surface of the firstseal element forms a dielectric side wall of the ring groove thattogether with the interior wall surface of the conductive ring contactelement define a physical stop for retaining the canted coil springinside the ring groove, and a portion of at least one of the sealelements projects into the conductive ring contact element.
 2. Theimplantable medical connector stack of claim 1, further comprising abore that is common to the conductive ring contact element and the firstand second seal elements.
 3. The implantable medical connector stack ofclaim 1, wherein the conductive ring contact element engages the firstseal element and the second seal element by projecting over a shoulderon each of the first seal element and the second seal element.
 4. Theimplantable medical connector stack of claim 1, wherein the conductivering contact element engages the first seal element and the second sealelement by projecting under a shoulder on each of the first seal elementand the second seal element.
 5. The implantable medical connector stackof claim 1, wherein the annulus of the first seal element comprises asecond projection.
 6. The implantable medical connector stack of claim1, wherein the stack is positioned inside an elastomeric or polymerheader.
 7. The implantable medical connector stack of claim 6, whereinthe header is attached to a sealed housing of an implantable medicaldevice.
 8. The implantable medical connector stack of claim 1, whereinthe conductive ring contact element comprises a bottom wall having aV-shape configuration.
 9. The implantable medical connector stack ofclaim 1, wherein the conductive ring contact element comprises anaxially extending wall that projects into a groove of the first sealelement and the generally planar wall surface of the first seal elementis positioned radially inwardly of the groove.
 10. The implantablemedical connector stack of claim 1, wherein the conductive ring contactelement comprises an axially extending wall that projects over ashoulder of the first seal element and under a shoulder of the secondseal element.
 11. The implantable medical connector stack of claim 1,wherein a lead conductor is welded to the conductive ring contactelement and is in electrical communication with a sealed housing of animplantable medical device.
 12. An implantable medical connector stackhaving easy to install ring grooves for receiving contact springscomprising: a conductive ring contact element comprising a first axialside, a second axial side, and a bottom wall having a V-shapeconfiguration; a first dielectric seal element in mechanical engagementwith the first axial side of the conductive ring contact element; asecond dielectric seal element in mechanical engagement with the secondaxial side of the conductive ring contact element; and wherein a ringgroove for accommodating a canted coil spring is formed by theengagements between the conductive ring contact element and the firstand second dielectric seal elements; and wherein at least part of thering groove has a first side wall formed by at least one of the firstdielectric seal element and the second dielectric seal element, and aportion of at least one of the dielectric seal elements projects intothe conductive ring contact element.
 13. The implantable medicalconnector stack of claim 12, wherein at least part of the ring groovehas a second side wall formed by the other one of the first dielectricseal element and the second dielectric seal element.
 14. The implantablemedical connector stack of claim 12, further comprising a bore that iscommon to the conductive ring contact element and the first and seconddielectric seal elements.
 15. The implantable medical connector stack ofclaim 12, wherein the conductive ring contact element projects over ashoulder on each of the first and second dielectric seal elements. 16.The implantable medical connector stack of claim 12, wherein theconductive ring contact element projects under a shoulder on each of thefirst and second dielectric seal elements.
 17. The implantable medicalconnector stack of claim 12, wherein the first dielectric seal elementcomprises an annulus comprising a projection.
 18. The implantablemedical connector stack of claim 12, wherein the stack is positionedinside an elastomeric or polymer header.
 19. The implantable medicalconnector stack of claim 18, wherein the header is attached to a sealedhousing of an implantable medical device.
 20. The implantable medicalconnector stack of claim 12, wherein the conductive ring contact elementcomprises an axially extending wall that projects into a groove of thefirst dielectric seal element.
 21. The implantable medical connectorstack of claim 12, wherein the conductive ring contact element comprisesan axially extending wall that projects over a shoulder of the firstdielectric seal element and under a shoulder of the second dielectricseal element.
 22. The implantable medical connector stack of claim 12,wherein a lead conductor is welded to the conductive ring contactelement and is in electrical communication with a sealed housing of animplantable medical device.
 23. The implantable medical connector stackof claim 12, further comprising two or more conductive ring contactelements.
 24. A method for forming an implantable medical connectorstack having easy to install ring grooves for receiving contact springscomprising: positioning a canted coil spring into a conductive ringcontact element; positioning the conductive ring contact element intoengagement with a first dielectric seal element; positioning theconductive ring contact element into engagement with a second dielectricseal element; wherein a groove comprising a bottom wall and two sidewalls is formed by the engagement between the conductive ring contactelement and both the first and second dielectric seal elements; andwherein at least one of the two side walls is formed by part of thefirst dielectric seal element or the second dielectric seal element, anda portion of at least one of the dielectric seal elements projects intothe conductive ring contact element.
 25. The method for forming animplantable medical connector stack of claim 24, further comprising thestep of placing a second conductive ring contact element into engagementwith the second dielectric seal element.
 26. The method for forming animplantable medical connector stack of claim 24, further comprising thestep of placing the stack into a header made from a polymer or anelastomer material.
 27. The method for forming an implantable medicalconnector stack of claim 24, further comprising the step of attachingthe header to a sealed housing of an implantable medical device.
 28. Amethod for forming a connector stack for an implantable medical devicehaving reduced overall length comprising: inserting a tubular ringcontact element into two adjacent seal ring elements to form a ringgroove; placing a spring into said ring groove; wherein the seal ringelements form at least one side wall of two successive ring grooves, theseal ring elements each comprising an annular projection for forming aseal against a lead body; and wherein the tubular ring contact elementis inserted into an interior shoulder of one of the two adjacent sealring elements.
 29. The method of claim 28, wherein the tubular ringcontact element is inserted over an exterior shoulder of at least one ofthe two adjacent seal ring elements.
 30. The method of claim 28, whereinthe two adjacent seal ring elements each comprises an annulus and atleast one projection defining an interior diameter.